Starter for electric motors.



W. C. OBRIEN & G. H. WHITTINGHAM.

STARTER POR ELECTRIC MOTORS. APPLICATION `FILED APB. 9,1907.

Patented July 26, 1910.

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UNITED sTATEs PATENT oEEioE.

WILLIAM C. OBRIEN lAND GEORGE H. WHITTINGHAM, OF BALTIMORE, MARYLAND, ASSIGNORS TO MONITOR MANUFACTURING COMPANY OF BALTIMORE CITY, A

CORPORATION OF MARYLAND.

STARTER FOR ELECTRIC MOTORS.

Specification of Letters Patent.

Patented July 26, 1910.

Application led April 9, 1907. Serial No. 367,193.

To all whom 'it may concern:

Be it known that we, WiLLLiM C. OBRIEN and GEORGE H. WHI'ITINGHAM, citizens of the United States, residin at Baltimore, in the State of Maryland, ave invented certain new and useful Improvements in Starters for Electric Motors, of which the following is a specification. This invention relates to improvementsin automatic starters for electric motors, of

l the kind in which thecutting out of the dicate solenoids mountediii -a suitable metall frame a and arranged arallel with` one another. Levers D and are pivoted in bearings a and a2 which depend from the lower cross bar of the frame, as shown. One end of the lever D is ivoted to the core 1 of the solenoid C andP one end of the lever E is pivoted to the core 2 of the solenoid C.v

The op osite ends of the levers extend beneath 'die core 3 of the solenoid B. The cores 1 and 2, asshown, are tubular so as to be lighter than the core 3, which is of solid metal; The relative weights of the cores aresuch that when the core 3 rests upon free ends of the levers it will overbalance the combined weights of the cores 1 and 2 so that the latter cores will be held in their upper and most eective positions within the coils of the solenoid C and C', as shown in Fig. 1. Switch arms 4 and 5 are inteally connected to the switch levers D and respectively, so that these arms will rock with the levers into and out of engagement vwith stationary switch members 6 and 7, respectively.

When the arts are in their normal positions, shown 1n Fig. 1',-the several solenoids are connected in series with one another and With the entire starting resistance and with the motor armature. From terminal 8 of the line switch in Fig. 1 the circuit through A the starter extends by conductors 9 and 10 to the coils of the solenoid B, which may be called the holdin solenoid, thence by conductors 11, 12, an 13 tothe coils of the regulating solenoid C, thence through conductor 14 and one section R of the starting resistance to the coils ofthe regulating sof lenoid C', thence through conductor 15 and section R of the starting resistance to conductor 16 which leads to one brush of the motor armature m. From the opposite brush of the motor armature the circuit eX- tends through conductors 17 and 18 to the line switch terminal 19. The terminals of the motor field coils are, as shown, connected by conductors 20A and 21 to the conductors 9 and 18, ectively, which lead to the lline switch terminals. The switch arms 4 and 5 are connected to the armature circuit by the wire 12, which, as shown is grounded upon the frame of the starter. The stationary switch member is connected by a conductor 22 to an intermediate point of the coils of the solenoid C', and the stationary switch member 7 is connected by the conductor 23 to the conductor 16 which leads to the armature,

The solenoids are all wound with wires'of low resistance capable of carrying the full armature current. The solenoid C has a greater length of wire in its coils than thc solenoid C, and, therefore, a greater-at- -tractive power over its core than has the solenoid C, with given current. When the line switch is open the parts remain as 1n Fig. 1, with the switches s and s2 o en and the resistances and the .coilsof al of the Y solenoids in series with the armature. When the line switch is closed the core of the solenoid B is drawn up into engagement with the magnet core 24, as shown in Fig. 2 where it remains while the motor is in operation. As soon as the current in the y armature circuit falls to a predetermined quantity, by reason of the acceleration of the armature, the core of the weaker solenoid C drops, and the lever D is thusrocked to close the switch s', as shown in Fig. 2. The solenoid C and resistance section. R, and a part of the windings of solenoid lC are thereby short circuited, the armature cur-` from the line terminal rent then passing solenoid B to conductor around the coils of 11 and the frame of the starter, thence line terminal 19 by way of conductor 1S.

The conductor 22 leading from the switch contact 6 is connected to the coilof solenoid C at a point which will cause a suieientA length ot' wire on the solenoid to be short circuited, when the switch s closes, to weaken the solenoid so that its core will drop when the current decreases to a point where it is desirable and safe to cut out the remaining section of the resistance. The

downward movement of the core of the solenoid C rocks the lever E and closes the switch si. A shunt is thus formed around the coils of solenoid C and the resistance section R. The armature current then iiows from the conductor 11 through switch arm 5, contact 7 and conductors 23 and 1G tothe armature, instead of through the solenoid coils and resistance. lVhen the line switch 1s opened the coils of solenoid B being thus denergized, the core of said solenoid drops onto the adj acentends of the levers D and E and rocks the levers to open the switches s and si', thus rcinserting the resistance scctions and the coils of solenoids C and C in the armature circuitand moving the cores of said solenoids to their upper positions.

It is not necessary to have the solenoid B, in the above described starter, connected in series with the armature, as this solenoid may be connected in any suitable way so as to be energized when the current is turned on at 'the line switch; 'but it is preferably arranged in series, as shown.

Various forms of magnets with movable cores or armatures may obviously be used to carry out the invention, although the solenoid form is preferred. For convenience, the devices which regulate the closing of the switches according to the quantity of current flowing in the armature 'circuit will be referred to in the claims as the regulating solenoids or devices, and the device which controls the movement of the switches to open position when current is eut off -will be referred to as the holding solenoid or device. Y

We c1aim,-

1. In an automatic starter for electric motors, a starting resistance in theV armature circuit, two regulating solenoids having their windings in said circuit, one of said solcnoids being wound so that its core will be released when the current in the armature circuit falls below a predetermlned'quantity, and the other being wound to support its core with less than thesaid quantity ofcurrent owing, a circuit for shnnting the; coils of the weaker solenoid and a sectioniof the startingresistance and a portion of the windings ofthe stronger solenoids, and a holding solenoid having a corel' adapted to norlnally bear upon said levers and ovcrbalance the cores ot' said regulating solenoids, thereby holding the switches no1 mally in open positions.

2. In an automatic starter for electric motors, a starting resistance in the armature circuit, two regulating solenoids having their windings Vin said circuit, one of said solenoids being wound so that its core will be released when the, current in the armature circuit falls below a predetermined quantity, and the other being wound to support its core with less than the said quantity ol current flowing, a circuit for shunting the coils of the weaker solenoid and a section of the starting resistance and a portion I of the windings ot' the stronger solenoid, a switch in said shunt circuit adapted to be closed by the movement of the core of said weaker solenoid when released from it's coils, a circuit for shunt-ing the remaining coils of said stronger solenoid and a section of the starting resistance, a switch in said latter circuit adapted to be closed by the movement of the core of said stronger solenoid when released from its coils, levers engagingthe cores of said regulating solenoids, and a holding solenoid having windings in the armature circuit and having a core adapted to normally bear upon said levers and over-balance vthe cores ot said regulating solenoids, thereby holding the switches normally in open positions.

3. An automatic starter for electric motors comprising a starting resistance in the armature circult, two electro-magnetic regulating devices having their windings in said circuit, one of said devices being arranged so that its core or armature will be released when.the current in the armature circuit falls below a predetermined quantity, and the other being wound to support its core or armature with less than the said quantity of current flowing, a circuit for shunting the coils of the weaker device and a section of the starting resistancel and a portion of the windings of the stronger device,'a switch in said shunt circuit adapted to be closed by the movement 'ofthe' core or armature -of said weaker device when released from its coils, a circuit for shunting the remaining coils of said stronger device anda section of the starting. reslstance, a switch in said latter circuit adapted to be closed by the movement of the core or armature of said stronger device when released from its coils, levers engaging-the cores or armatures of said regulating devices, and a holding device havin a core or armature adapted to normally ear upon said levers and over-balance the cores or armatures of .said regulating devices, thereby holding the switches normally in open positions.

4. An automatic starter for electric motors comprising a starting resistance in the armature circuit, two electro-magnetic regulati'ng devices having their windings in said circuit, one of said devices being arranged so that its core or armature will be released when the current in the armature circuit falls below a predetermined quantity, and the other being wound to support its core or armature with less than the said quantity of current flowing, a circuit for shunting the coils of the weaker device and a section of the startingrresistance and a portion of the windings of the stronger device, a switch in said shunt circuit adapted to be closed by the movement of the core or armature of said weaker device when released from its coils, a circuit for shunting the remaining coils of said stronger device and a section of the starting resistance, a switch in said latter circuit adapted to be closed by the movement of the core or armature of said stronger device when released from its coils, levers engaging the cores or armatures of said regulatin device, and a holding device having win ings in the armature circuit and having a core or armature adapted to normally bear upon said levers and overbalance the cores or armatures of said regulating devices, thereby holding the switches normally in open position.

In testimony whereof we afiix our signatures, in resence of two witnesses.

W LLIAM C. OBRIEN.

GEORGE H. WHITTINGHAM.

Witnesses:

ROBERT WATSON, CLAY JEWELL. 

